Plate margins and plate tectonics
Earthquakes and volcanic eruptions affect people all over the world. They are caused by the movement of tectonic plates. Tectonic hazards can destroy buildings, infrastructure and cause deaths.
The Earth's structure and plate tectonics
The Earth is made up of different layers:
- The inner core is in the centre and is the hottest part of the Earth. It is solid and made up of iron and nickel with temperatures of up to 5,500°C.
- The outer core is the layer surrounding the inner core. It is a liquid layer, also made up of iron and nickel.
- The mantle is the thickest section of the Earth at approximately 2,900 km. The mantle is made up of semi-molten rock called magma.
Demonstrating the movement of the Earth's crust and how tectonic plates interact at plate margins
The theory of plate tectonics
The crust is the outer layer of the Earth. It is a thin layer between 0 - 60 km thick. The crust is the solid rock layer upon which we live. It is either continental or oceanic. The earth's crust is broken into plates. It was once believed that convection currents in the mantle slowly moved the crust around. It is now thought that a mechanism called slab pull drives the movement of tectonic plates. Slab pull occurs where older, denser tectonic plates sink into the mantle at subduction zones. As these older sections of plates sink, newer and less dense sections of plate are pulled along behind. Sinking in one place leads to plates moving apart in other places.
The movement of the plates, and the activity inside the Earth, is called the theory of plate tectonics.